Question

Assertion: Iodine shows oxidation state of $+ 1$ and $+ 3$ in the compounds ICl and ${\rm{IC}}{{\rm{l}}_{\rm{3}}}$ respectively.
Reason: Iodine coming below the halogens F, Cl and Br in the halogen group of elements in the periodic table shows a higher degree of electropositive nature.
A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion.
B. Both Assertion and Reason are correct and Reason is not the correct explanation for Assertion.
C. Assertion is correct but Reason is incorrect.
D. Both Assertion and Reason are incorrect.

Answer 1

If we move down in a group of periodic tables, the size of the element increases along with electropositive character whereas it decreases on moving along the period. Halogens are highly electronegative due to the requirement of one electron to obtain noble gas configuration.

Complete step by step answer:
We know that fluorine, chlorine, bromine and iodine are halogens and belong to the group number 17. The general electronic configuration of halogens is ${\rm{n}}{{\rm{s}}^{\rm{2}}}{\rm{n}}{{\rm{p}}^{\rm{5}}}$. We can see that to complete its p orbital halogens require only one electron. Due to this, their electron gain enthalpy is maximum follows the order ${\rm{Cl}} > {\rm{F}} > {\rm{Br}} > {\rm{I}}$. Therefore, halogens are electronegative in nature.
To answer the problem we need to learn about the concept of electropositivity. Electropositivity increases down the group because the effective nuclear charge decreases and atomic size increases down the group while electropositivity decreases on moving in the period.
As we move the electronegativity of the element decreases because the size of the element increases. Chlorine (Cl) is more electronegative than iodine (I), therefore the oxidation state of Iodine in ICl is $+ 1$ and in ${\rm{IC}}{{\rm{l}}_{\rm{3}}}$ is $+ 3$. Hence, the Assertion is correct.
We have already learnt that the electropositive character increases on moving down the group in the periodic table. Therefore, the Assertion is also a correct statement and a correct explanation for Assertion.
So, the correct answer is “Option A”.

Note:
We need to remember that down the group the stability of higher oxidation states increases while decreasing on moving left to right in a period from group 3 to group 8 and not observed in the later groups.